A little while back, I did an article on the importance of lichens for deer, and other wildlife, I’m posting it below, for context as to why I’m predicting large losses of deer here this winter.
The last time the area I live in had a winter this severe – about 20 years ago – the forest was strewn with dead and dying balsam trees, most of them laden with lichens. Although deer south of here suffered terribly, the deer around me came through the winter in much better shape than most envisaged, and what the models were suggesting. I and others thought the reason was the abundance of lichens – where lichens were rare, deer losses were much higher than in those deer wintering areas where lichens were abundant (south of here, the forests where deer thrive are poplar and cedar, with little lichen. North of here deer numbers have never been high, it’s just too far north and winters are on average, too severe).
Now, it’s another bad winter, but the forest around me has little lichen. I think a large deer die-off is imminent.
They’re Lichen It!
By Bruce Ranta
Lichens (pronounced ‘likens’) are an important food source for many species of wildlife. Squirrels, beavers and even groundhogs relish a meal of lichen. Lichens are also a source of food for Ontario’s cervids, namely whitetail deer, moose, elk and caribou. Indeed, lichens can be the key ingredient behind population fluctuations of caribou and deer on many northern ranges.
Aside from the fact it’s a favourite winter forage, the lichen is an interesting plant. Lichens are an example of a perfect symbiotic relationship, a case where two different species depend on each other for survival. So a lichen is a plant made up of tens of thousands of individuals of two other plants, one an algae and one a fungus, united together. How algae and fungi fit together to form lichens – including many different species of lichens – is still mostly a mystery.
There are three major types of lichens. Foliose lichens are leaf-like in appearance, fruticose are shrubby or hair-like, while crustose look crusty. A fourth group, known as squamulose, are small and don’t have certain vegetative structures found on the others. Only foliose and fruticose lichens are large enough to be a meaningful source of food for wildlife.
Lichens are relatively slow growing. The fastest growing species are mostly fruticose lichens that grow on trees, referred to as arboreal lichens. These species can put on about an inch a year. All lichens grow as a result of self-manufactured food intake through photosynthesis. They also absorb nutrients from rainwater and from whatever they are attached to. They thrive in cool damp climates and do poorly in areas that are hot and dry. They reproduce and colonize mainly by a process called vegetative propagation, which means when a piece breaks off, that fragment can start a new plant. Lichens are very susceptible to air pollutants and can die and disappear where air quality is poor.
As forage for ungulates, lichens are believed to be at least as nutritious as most woody browse, although standard forage analysis results in questionable results. Still, lichens are known to be rich in micro-nutrients, some of which may play an important role in helping to deal with the stress of a long, cold winter. It’s also thought that lichens might act as a carbohydrate resource, increasing the efficiency of urea cycling and helping deer, for example, maintain a higher amount of body water than they can on a steady diet of twigs and buds. Theoretically, that would help combat cold.
It’s long been known that in winter, caribou eat little else but lichen. Their preference are ground fruticose lichens, appropriately enough called caribou ‘moss’, which upon inspection actually look like caribou antlers. Caribou also eat arboreal lichens, as do white-tailed deer, elk and moose. While ground lichens can be very abundant on exposed rock ridges and open, lightly stocked conifer forests, only caribou feed heavily on ground lichens.
Arboreal fruticose lichens can be unbelievably abundant. This is particularly true in northern forests where conifer forests of spruce and balsam fir predominate. In healthy spruce and fir forests, there isn’t much for deer to eat during the winter, and deer populations tend to be low. However, when there are huge swaths of dead and dying conifers in the aftermath of a spruce budworm epidemic, deer populations can skyrocket. That’s because budworm outbreaks create ideal conditions for arboreal lichens, especially for a group of lichens biologists call Usnea, more commonly known as ‘gray beard’ or ‘old man’s beard’.
A typical spruce budworm outbreak occurs over tens of thousands of square kilometers and results in millions of dead and dying fir and spruce. These dead and dying trees quickly become colonized by Usnea, to the point where a stand of dead fir will still look green and healthy to casual observers. In such situations, the lichens are by far the most abundant living plant in the forest.
Lichen laden forests of dead balsam (spruce don’t suffer as much mortality from budworm as do balsam) are a boon to wintering whitetails, sometimes for years. Lichens in budworm ravaged forests can be so lush deer can find plenty of food even during heavy snow winters simply by jumping from one dead tree to the next. Eventually, though, the dead balsam fall down and are vacuumed clean by herds of hungry deer. I’ve killed several deer whose rumens were full of arboreal lichen and little else.
Moose and elk feast on Usnea as well, but caribou don’t seem to like it as much as they do other species. Caribou prefer arboreal lichens like Alectoria and Bryoria, hairy looking, dark coloured species that in Ontario, grow mostly on black spruce.
Spruce budworm epidemics occur regularly on about a 40 year cycle. In northwestern Ontario, the last outbreak started up about 1980 and took over 10 years to run its course. The next outbreak in the region isn’t scheduled until about 2020. Interestingly, deer numbers around Kenora peaked about 2007, and in a forest where lichens are now much reduced, deer are now definitely trending down.
Although old man’s beard and other arboreal lichen species aren’t as abundant in a healthy forest as they are in one with oodles of dead and dying trees, they’re still there and supplement the winter diet of all the cervids. Many trees have some lichens growing on their trunks, while other trees, such as large spruce, are often laden with lichens. While much of the lichen biomass might be high in the tree and out of reach of animals, there’s always some that can be gleaned from the lower branches. High winds can also provide deer with otherwise unavailable lichens by blowing them free, breaking off branches and knocking over trees.
Foliose lichens – the ones that look like leaves – also provide cervids with a winter food source. One type of foliose lichen, called rock tripe, is common on large rocks and rock faces that are regularly wetted or are in some sort of damp micro-climate, like along lake and river shorelines. On the lower French River, elk foraging on rock tripe on such shorelines have made a noticeable ‘browse line’. Adult elk from that area can actually be identified by their worn down front teeth, a testimonial to how much grazing on rock tripe they do each winter.
When I’m hunting deer late in the season, I always keep an eye out for areas with blowdown, or even individual trees that have recently fallen. These can be magnets for deer looking to fill their bellies, and offer excellent opportunities to jump deer or set up a stand and wait for the dinner bell to ring. I recall setting up on a knoll one afternoon in late November beside a clump of dead balsam, encrusted with lichens that had fallen over in a recent windstorm. Within a half hour, there were three bucks munching on the lichens, one within 10 feet of me.
Looking for lichens won’t necessarily put you on animals, but being aware of just how fond all deer are of this strange little plant could be what helps you bring home the venison some years.
Me? I’m waiting patiently for the next big spruce budworm epidemic.